1. Field of the Invention
The present invention relates to a method of data storage systems, and particularly related to storage of special data sets that reside on a single logical volume in a volume group.
2. Description of the Related Art
Data handled by storage systems managed by business organizations, local authorities, public offices, financial institutions etc. increases year by year on the one hand, while new storage apparatus (e.g. hard disk drives) are added to or exchanged with existing storage apparatus in accompaniment with increase in the amount of data. When a plurality of storage apparatus are added to a storage system in accompaniment with an increase in the amount of data to be managed, configuration of the storage system becomes complex. Virtualization of a storage system is well known as technology for resolving this kind of problem. Virtualization of the storage system is technology where a plurality of storage apparatus mutually connected to a network are virtualized logically as a single storage system. By virtualizing the storage system, operations management can also be handled jointly as one, and this may contribute towards a reduction in management costs.
To virtualize a single storage system, logical volumes are created that typically reside on one or more of the physical storage apparatus. A volume group specifies a set of multiple logical volumes.
Space is allocated in the volume group from among the logical volumes to accommodate new data sets. Most data sets can spread across the logical volumes. However, certain special data sets must reside on a single logical volume within the volume group. Thus, when a data set of this type is allocated to a volume group that allocation may fail because no single logical volume has sufficient space for the special data set even though the volume group has sufficient storage capacity. Certain kinds of these special data sets are critical to the operation of the storage system. A failure to allocate such critical special data sets can result in storage system outages.